In the research field of ocean engineering, either design of offshore oil drilling platforms, development of ocean power generation apparatuses or pavement of submarine pipelines and construction of marine safety engineering, the research phase of a laboratory is often indispensable, i.e., an experimental model is required to be placed in wave current tanks and pools for design verification. A wave maker is an essential experimental instrument device[1-4] in this process. The device can simulate many types of wave forms in the ocean within a limited space, and can provide a simulation environment of experimental verification for development of marine equipment.
In the process of simulating a wave, a plurality of wave paddles in a wave making system are synergistically controlled to move, thereby producing different wave forms. However, regardless of push paddle type wave making or shake paddle type wave making, the control principles are consistent: firstly, wave simulation parameters are set for a target spectrum; the host computer computes a control signal of a time sequential value for operating each wave paddle according to a transfer function of the system; and meanwhile, the signal is transmitted to a corresponding slave computer through a dedicated network. After the slave computer receives the control signal of the host computer, a wave making program is started to begin wave making. The slave computer converts the control signal of the time sequential value for operating each wave paddle into an irregular position pulse control signal through a dedicated motion control interface, outputs to a servo power supply and also drives a servo actuator to drive the wave paddle to make corresponding movement, thereby pushing a water body to produce waves. A servo motor encoder measures a motion track of a push paddle in real time, and feeds back to the servo power supply, so as to ensure that the wave push paddle can accurately track a computer-given signal for operation. The feedback signal is also fed back to the motion control interface. The slave computer can accordingly monitor the operating state of the wave paddle for inquiry by the host computer.
It is observed from the above operation mechanism of the wave maker that the moving mass of the wave paddle directly affects the quality of wave simulation and reasonableness of the wave making experiment. Meanwhile, it can be seen that when a failure occurs in operation of the wave paddle, a driver gives an alarm to the slave control computer, and the slave computer notifies the host computer of an error number while stopping the operation of the motor controlled by the computer. After the host computer receives the failure, all the slave computers are stopped and a failure type is displayed at the time of alarming. However, this is a failure processing manner under normal conditions. In a maritime engineering experiment, the wave maker is operated for a long time. Under some conditions, when the driver is damaged or a control program exits abnormally, the host computer cannot obtain an error message due to disconnection among programs of an application layer, but still can continue to make the waves. In this case, wave data in an experimental pool is not accurate; an experimental conclusion is invalid; and instant shutdown is needed. However, for the present wave making control system, a data transmission manner from the slave computer to the host computer through information feedback from the encoder or a displacement sensor is used. This failure feedback manner is completely integrated in a control loop. Once an abnormal situation appears, an experimenter controlling the host computer cannot obtain the failure message in time, causing a decrease of experimental efficiency. Thus, a monitoring method for the operating state of the wave maker is needed to test and assess an operating wave making state in real time. A video monitoring method not only is independent of the wave making control system, but also has the features of convenient installation, no contact and full-field measurement. Therefore, this method is suitable for monitoring in a wave making site.